This R03 application examines how perception of strength and balance is altered by decreased arousal following stroke. Stroke affects 600,000 patients annually in the United States. Perception of limb strength may be altered in half of all stroke patients. One-third of all stroke patients fall during stroke rehabilitation. Falling is related to altered strength and balance. The long term goal of this study is to improve the outcome of stroke rehabilitation by treating arousal-related deficits that impede progress in therapy and lead to complications. Whereas the neglect syndrome following right hemisphere stroke is known to be associated with altered arousal and perception, this project aims to show that altered perception of strength and balance is much more common than neglect and that rehabilitation is complicated by deficits in arousal even in patients without neglect. Aim I will validate the constructs of altered strength and balance perception by demonstrating their relationship to functional limitations. Aim II will test the link between altered arousal, perception and function by using caloric stimulation to temporarily increase arousal in stroke patients. Aim III examines whether patients with the capacity to respond to caloric stimulation have better functional outcomes three months after rehabilitation than those who do not. This research is intended to lay the ground-work for pharmacological studies that use arousal-enhancing medications to treat perceptual deficits in stroke patients during rehabilitation. This proposal aims to improve public health in the US by rehabilitating altered perception of contralateral limb strength following stroke. Altered perception of strength may be a significant contributor to poor participation and frustration in rehabilitation therapy and it increases the risk of orthopedic injury due to falls. Stroke affects 600,000 patients annually in the United States. Half of all stroke patients in rehabilitation may have altered strength perception. There is no pharmacological treatment at the present time.